WO2015093419A1

WO2015093419A1 - Gear transmission device

Info

Publication number: WO2015093419A1
Application number: PCT/JP2014/083057
Authority: WO
Inventors: 薫四十
Original assignee: ナブテスコ株式会社
Priority date: 2013-12-16
Filing date: 2014-12-12
Publication date: 2015-06-25
Also published as: DE112014005706T5; US20160319907A1; TW201901063A; CN109027137B; TWI701398B; JP2015113974A; CN109027138B; CN105829761B; TWI654383B; CN109027137A; TW201537065A; CN109027138A; KR20160099632A; DE112014005706B4; JP6194241B2; KR102280615B1; US10001195B2; CN105829761A

Abstract

This gear transmission device comprises a crank shaft, an eccentric rotation gear, and a self-rotating gear. The eccentric rotation gear rotates eccentrically in association with the rotation of the crank shaft. The self-rotating gear meshes with the eccentric rotation gear. The crank shaft includes a shaft part, a first eccentric part, and a second eccentric part. The first eccentric part engages with the eccentric rotation gear. The second eccentric part is provided between the shaft part and the first eccentric part. The rotation axis of the first eccentric part is offset from the rotation axis of the shaft part by a first distance. The rotation axis of the second eccentric part is offset from the rotation axis of the shaft part by a second distance. The second distance is smaller than the first distance.

Description

Gear transmission

This application claims priority based on Japanese Patent Application No. 2013-259268 filed on Dec. 16, 2013. The entire contents of that application are incorporated herein by reference. This specification discloses the technique regarding a gear transmission.

2. Description of the Related Art A gear transmission device that includes an eccentric rotating gear that rotates eccentrically and a rotating gear that meshes with the eccentric rotating gear and that has a number of teeth different from the number of teeth of the eccentric rotating gear is known. In such a gear transmission, an eccentric rotation gear is eccentrically rotated using a crankshaft. The eccentric rotating gear is provided with a through hole, and the crankshaft is provided with an eccentric portion. The eccentric portion is disposed in the through hole of the eccentric rotating gear. A bearing (hereinafter referred to as a first bearing) is disposed between the eccentric portion and the through hole. In the gear transmission disclosed in Japanese Patent Laid-Open No. 5-180278, a washer is attached to the shaft portion of the crankshaft to restrict the first bearing from moving in the axial direction.

In the gear transmission of Japanese Patent Laid-Open No. 5-180278, a washer is attached to the shaft portion of the crankshaft. That is, the washer is attached coaxially with the shaft portion, and is not attached coaxially with the eccentric portion. Therefore, when the crankshaft is observed from the axial direction, the length of the washer projecting outside the eccentric portion varies depending on the circumferential position of the eccentric portion. In order to restrict the movement of the first bearing in the axial direction, it is necessary to position the outer periphery of the washer outside the outer periphery of the eccentric portion. Since the washer and the eccentric portion are not coaxial, in order to position the outer periphery of the washer outside the outer periphery of the eccentric portion, it is necessary to increase the outer diameter of the washer. However, when the outer diameter of the washer is increased, a part of the washer protrudes to the outside of the outer periphery of the first bearing, and the washer may interfere with other parts. On the contrary, when the outer diameter of the washer is adjusted so that the washer does not protrude outside the outer periphery of the first bearing, a range in which the washer does not protrude outside the outer periphery of the eccentric portion becomes wide. As a result, the washer may not be able to regulate the movement of the first bearing. The present specification solves the above-described problems and discloses a technique for more reliably regulating the movement of the first bearing in the axial direction.

The gear transmission disclosed in this specification includes a crankshaft, an eccentric rotating gear, and a rotating gear. The eccentric rotating gear rotates eccentrically with the rotation of the crankshaft. The rotation gear meshes with the eccentric rotation gear, and has a number of teeth different from the number of teeth of the eccentric rotation gear. The crankshaft includes a shaft portion, a first eccentric portion, and a second eccentric portion. The first eccentric portion is provided in the middle of the shaft portion and is engaged with the eccentric rotation gear. The second eccentric part is provided between the shaft part and the first eccentric part. In the gear transmission disclosed in the present specification, the first rotating shaft of the first eccentric portion is offset by a first distance from the rotating shaft of the shaft portion, and the second rotating shaft of the second eccentric portion is the rotating shaft of the shaft portion. Is offset by a second distance, and the second distance is smaller than the first distance.

According to the above gear transmission, by attaching a washer to the second eccentric part, the washer can be offset from both the rotation axis of the shaft part and the rotation axis (first rotation axis) of the first eccentric part. More specifically, the washer can be attached to the crankshaft with an eccentric amount smaller than the eccentric amount of the first eccentric portion with respect to the shaft portion. Compared with the case where a washer is attached to the shaft portion, it is possible to ensure a wide range in which the washer protrudes outside the outer periphery of the first eccentric portion while maintaining the size (outer diameter) of the washer small.

If the second eccentric portion is offset from the rotation axis of the shaft portion by the same amount as the first eccentric portion (if the second distance is the same as the first distance), the washer is placed outside the outer periphery of the first eccentric portion. The protruding length is equal in the circumferential direction of the first eccentric portion. Therefore, it can be expected to further reduce the size of the washer. However, if the second distance is the same as the first distance (the second eccentric portion is coaxial with the first eccentric portion), the amount of washer eccentricity with respect to the shaft portion increases. As a result, a part that restricts the movement of the washer (a part that keeps the washer in the second eccentric portion) may not come into contact with the washer. If the washer moves in the axial direction, as a result, the movement of the first bearing in the axial direction cannot be restricted. The above gear transmission can more reliably regulate the movement of the first bearing in the axial direction by making the second distance smaller than the first distance.

Sectional drawing of the gear transmission of an Example is shown. The expanded sectional view of the part enclosed with the broken line II of FIG. 1 is shown. The figure for demonstrating the characteristic of the gear transmission of an Example is shown. The figure for demonstrating the characteristic of the conventional gear transmission is shown. The figure for demonstrating the characteristic of the gear transmission of a comparative example is shown.

Hereinafter, some of the technical features of the gear transmission disclosed in this specification will be described. The items described below have technical usefulness independently.

The gear transmission includes a crankshaft, an eccentric rotating gear, and a rotating gear. The eccentric rotating gear may rotate eccentrically with the rotation of the crankshaft. The rotation gear meshes with the eccentric rotation gear, and may have a number of teeth different from the number of teeth of the eccentric rotation gear. The eccentric rotation gear may be an external gear, and the rotation gear may be an internal gear. Alternatively, the eccentric rotation gear may be an internal gear, and the rotation gear may be an external gear. When the eccentric rotation gear is an external gear, a carrier that rotates relative to the internal gear may be provided. The case surrounding the outer side in the radial direction of the external gear may also serve as the internal gear. In this case, the crankshaft may be rotatably supported by the carrier. The shaft portion of the crankshaft may be supported by the carrier via a bearing. When the eccentric rotation gear is an internal gear, a case may be provided that encloses the radially outer side of the internal gear. In this case, the crankshaft may be rotatably supported by the case. The shaft portion of the crankshaft may be supported by the case via a bearing.

The crankshaft may have a shaft portion, a first eccentric portion, and a second eccentric portion. The first eccentric part may be provided in the middle of the shaft part. In other words, the shaft portion may extend from the first eccentric portion in both the axial directions of the crankshaft. The first eccentric portion may be engaged with the eccentric rotating gear. A through hole is formed in the eccentric rotating gear, and the first eccentric portion may be engaged with the through hole through a bearing (first bearing). That is, the first bearing may be disposed between the first eccentric portion and the eccentric rotating gear. The first bearing may be a cylindrical roller bearing. The first rotation axis of the first eccentric portion may be offset by a first distance from the rotation axis of the shaft portion. The first rotation axis may extend parallel to the rotation axis of the shaft portion. When the crankshaft rotates, the first rotating shaft rotates around the rotating shaft of the shaft portion.

The second eccentric part may be provided between the shaft part and the first eccentric part. The second rotation axis of the second eccentric portion may be offset by a second distance from the rotation axis of the shaft portion. The second distance may be different from the first distance. Further, the second distance may be smaller than the first distance. The second rotation axis may extend parallel to the rotation axis of the shaft portion. When the crankshaft rotates, the second rotating shaft rotates around the rotating shaft of the shaft portion. The second rotating shaft may be located between the rotating shaft of the shaft portion and the first rotating shaft. That is, when the crankshaft is observed from the axial direction, the rotation axis, the first rotation axis, and the second rotation axis of the shaft portion may be arranged on a single straight line. In other words, the eccentric direction of the second eccentric portion relative to the shaft portion may be the same as the eccentric direction of the first eccentric portion relative to the shaft portion.

The diameter of the second eccentric part may be larger than the diameter of the shaft part and smaller than the diameter of the first eccentric part. Further, when the crankshaft is observed from the axial direction, the outer periphery of the first eccentric portion may be located outside the outer periphery of the second eccentric portion. Further, when the crankshaft is observed from the axial direction, the outer periphery of the second eccentric portion may be located outside the outer periphery of the shaft portion. A part of the outer periphery of the second eccentric part may be located outside the outer periphery of the shaft part, and the other part may overlap with the outer periphery of the shaft part. In the following description, “observing the crankshaft from the axial direction” may be referred to as “viewing in plan”.

A ring member may be attached to the second eccentric part. When the crankshaft is viewed in plan, the outer periphery of the ring member may be located outside the outer periphery of the first eccentric portion. In this case, the outer periphery of the ring member may be positioned outside the outer periphery of the first eccentric portion in the entire periphery, or a part thereof may be positioned outside the outer periphery of the first eccentric portion. Further, the ring member may overlap the first bearing when viewed in plan. In this case, the ring member may overlap with the first bearing along the entire circumference in the circumferential direction, or a part of the circumferential direction may overlap with the first bearing.

A second bearing having an inner ring, a rolling element, and an outer ring may be attached to the shaft portion. The crankshaft may be supported by the carrier or the case via the second bearing. The second bearing may be a type of bearing that restricts movement of the crankshaft in the axial direction and the radial direction. As such a bearing, a tapered roller bearing, an angular roller bearing, an angular ball bearing, or the like can be used. When viewed in a plan view, the outer periphery of the inner ring of the second bearing may be located outside the outer periphery of the second eccentric portion. In this case, the inner ring of the second bearing may be located outside the outer circumference of the second eccentric portion in the entire circumference in the circumferential direction, or a part of the circumferential direction is located outside the outer circumference of the second eccentric portion. It may be. Further, the inner ring of the second bearing may be in contact with the ring member.

The gear transmission 100 will be described with reference to FIG. In the following description, parts having substantially the same function may be described by omitting alphabetical symbols attached to reference numerals. The gear transmission 100 includes an internal gear 40, a carrier 2, a crankshaft 4, and an external gear 14. The internal gear 40 is an example of a rotation gear, and the external gear 14 is an example of an eccentric rotation gear. The internal gear 40 includes a case 38 and a plurality of internal gear pins 36. The case 38 surrounds the outer side of the external gear 14 in the radial direction. The internal tooth pin 36 has a cylindrical shape and is disposed on the inner peripheral surface of the case 38. The carrier 2 is rotatably supported by the case 38 by a pair of bearings 34. The pair of bearings 34 restricts the carrier 2 from moving in the axial direction and the radial direction with respect to the case 38. In the gear transmission 100, angular ball bearings are used as the pair of bearings 34. The internal tooth pin 36 is disposed between the pair of bearings 34.

The carrier 2 includes a first plate 2a and a second plate 2c. The first plate 2a includes a columnar portion 2b. The columnar portion 2b extends from the first plate 2a toward the second plate 2c, and is fixed to the second plate 2c. The crankshaft 4 is rotatably supported by the carrier 2 by a pair of bearings 8 (8a, 8b). A bearing 8a is attached to the first plate 2a, and a bearing 8b is attached to the second plate 2c. The pair of bearings 8 restricts the crankshaft 4 from moving in the axial direction and the radial direction with respect to the carrier 2. In the gear transmission 100, angular roller bearings are used as the pair of bearings 8. The pair of bearings 8 is an example of a second bearing. Hereinafter, the second bearing 8 (8a, 8b) may be referred to. Details of the second bearing 8 will be described later.

The crankshaft 4 includes two first eccentric portions 18 (18a, 18b). The first eccentric portion 18 is provided in the middle of the shaft portion 6 (6a, 6b). The shaft portion 6 is supported on the carrier 2 by a pair of second bearings 8. The first eccentric portion 18a is engaged with the external gear 14a via the bearing 16a. The first eccentric portion 18b is engaged with the external gear 14b via the bearing 16b. In the gear transmission 100, a cylindrical roller bearing is used as the bearing 16 (16a, 16b). The bearing 16 is an example of a first bearing. In the following description, the first bearing 16 (16a, 16b) may be referred to. The first bearing 16a is restricted from moving in the axial direction by the washer 12a and the first eccentric portion 18b. The washer 12a is an example of a ring member. The first bearing 16b is restricted from moving in the axial direction by the washer 12b and the first eccentric portion 18a. Details of the first bearing 16 will be described later.

The input gear 22 is fixed to the shaft portion 6b. The input gear 22 is fixed to the shaft portion 6 b outside the pair of second bearings 8. Torque of a motor (not shown) is transmitted to the input gear 22. When the motor torque is transmitted to the input gear 22, the crankshaft 4 rotates around the rotation shaft 30. When the crankshaft 4 rotates, the first eccentric portion 18 rotates eccentrically around the rotation shaft 30. As the first eccentric portion 18 rotates eccentrically, the external gear 14 rotates eccentrically while meshing with the internal gear 40. The external gear 14 rotates eccentrically around the axis 32 of the gear transmission 100. The first eccentric portion 18 a and the first eccentric portion 18 b are eccentrically symmetrical with respect to the rotation shaft 30. Therefore, the external gear 14 a and the external gear 14 b rotate eccentrically symmetrically around the axis 32.

The crankshaft 4 will be described in detail with reference to FIG. In the following description, the structure around the shaft portion 6a and the first eccentric portion 18a will be described. Since the structure around the shaft portion 6b and the first eccentric portion 18b is substantially the same as the structure around the shaft portion 6a and the first eccentric portion 18a, description thereof is omitted.

As shown in FIG. 2, the crankshaft 4 has a shaft portion 6a, a first eccentric portion 18, and a second eccentric portion 62. The rotating shaft 64 of the first eccentric portion 18 is offset from the rotating shaft 30 of the shaft portion 6 by a distance A1 (first distance). The rotation axis 66 of the second eccentric part 62 is offset from the rotation axis 30 of the shaft part 6 by a distance A2 (second distance). The offset amount (distance A2) of the rotary shaft 66 with respect to the rotary shaft 30 is smaller than the offset amount (distance A1) of the rotary shaft 64 with respect to the rotary shaft 30. The second eccentric portion 62 is provided between the shaft portion 6 a and the first eccentric portion 18 in the axial direction (the direction in which the rotation shaft 30 extends). The first eccentric portion 18 is disposed in the through hole 14 h of the external gear 14. A first bearing 16 is attached to the first eccentric portion 18. The first bearing 16 is fitted on the outer periphery of the first eccentric portion 18. The first eccentric portion 18 is engaged with the external gear 14 via the first bearing 16. The first bearing 16 includes a retainer 58 and a plurality of cylindrical rollers 60.

The second bearing 8 is disposed between the shaft portion 6 and the carrier 2. The second bearing 8 includes an inner ring 50, rolling elements (cylindrical rollers) 52, and an outer ring 54. The inner ring 50 is attached to the shaft portion 6a. Specifically, the inner ring 50 is fitted into the outer periphery 6s of the shaft portion 6a. The outer ring 54 is attached to the carrier 2. A stopper 56 is attached to the carrier 2 and is in contact with the outer ring 54 of the second bearing 8a. The stopper 56 restricts the outer ring 54 from moving outward in the direction of the rotation shaft 30 (on the side opposite to the side where the first eccentric portion 18 exists).

The rolling element 52 is disposed between the inner ring 50 and the outer ring 54. The rotating shaft of the rolling element 52 is inclined with respect to the rotating shaft 30 of the shaft portion 6. More specifically, the rotating shaft of the rolling element 52 is inclined so as to approach the rotating shaft 30 from the inner side in the direction of the rotating shaft 30 of the crankshaft 4 (the side where the first eccentric portion 18 exists) to the outer side. Yes. The pair of

second bearings

8a and 8b applies a preload that compresses the crankshaft 4 in the direction of the rotary shaft 30 (see also FIG. 1). The second bearing 8 restricts the crankshaft 4 from moving in the axial direction and the radial direction.

A washer 12 a is attached to the outer periphery 62 s of the second eccentric portion 62. The thickness of the washer 12 is substantially equal to the thickness of the second eccentric portion 62. The washer 12 is disposed between the first eccentric portion 18 and the inner ring 50. The first eccentric portion 18 and the inner ring 50 restrict the washer 12 from moving in the axial direction. The outer diameter of the washer 12 a is larger than the outer diameter of the first eccentric portion 18. Further, when the crankshaft 4 is observed from the direction of the rotary shaft 30, the entire circumference of the outer periphery 12 s of the washer 12 is located outside the outer periphery 18 s of the first eccentric portion 18. Further, the entire circumference of the outer periphery 12 s of the washer 12 is located inside the outer periphery 16 s of the first bearing 16.

FIG. 3 is a diagram showing the positions of the shaft portion 6, the first eccentric portion 18, the second eccentric portion 62, the first bearing 16, and the washer 12 when the crankshaft 4 is observed (plan view) from the direction of the rotation axis 30. It is. In addition, about the 1st bearing 16, detailed illustration is abbreviate | omitted and only the existence range is shown. As apparent from FIGS. 2 and 3, the

rotation shafts

64 and 66 extend in parallel to the rotation shaft 30. The rotation shaft 66 is located on a straight line connecting the rotation shaft 30 and the rotation shaft 64. That is, the first eccentric portion 18 and the second eccentric portion 62 have the same eccentric direction with respect to the shaft portion 6, and the amount of eccentricity of the second eccentric portion 62 with respect to the shaft portion 6 is the same as that of the first eccentric portion 18. It is smaller than the amount of eccentricity with respect to the shaft portion 6.

As shown in FIG. 3, the outer periphery 12s of the washer 12 is located outside the outer periphery 18s of the first eccentric portion 18 over the entire periphery. The washer 12 overlaps the first bearing 16 over the entire circumference. Specifically, the washer 12 overlaps the retainer 58 of the first bearing 16 over the entire circumference in the circumferential direction (see also FIG. 2). The washer 12 is in contact with the entire circumference of the first bearing 16 (retainer 58) in the circumferential direction, and can restrict the first bearing 16 from moving in the axial direction. Further, the outer periphery 12 s of the washer 12 is located inside the outer periphery 16 s of the first bearing 16. That is, the washer 12 does not overlap the external gear 14 when viewed in plan. (Does not interfere.)

The outer diameter of the second eccentric part 62 is larger than the outer diameter of the shaft part 6. Further, almost the entire outer periphery 62 s of the second eccentric portion 62 is located outside the outer periphery 6 s of the shaft portion 6. In other words, a part of the outer periphery 62s overlaps with the outer periphery 6s when seen in a plan view. The outer diameter of the second eccentric portion 62 is smaller than the outer diameter of the first eccentric portion 18. Further, the entire outer periphery 62 s of the second eccentric portion 62 is located inside the outer periphery 18 s of the first eccentric portion 18. Therefore, when the washer 12 is attached to the second eccentric portion 62, the entire circumference in the circumferential direction of the washer 12 is in contact with the first eccentric portion 18. The inner ring 50 of the second bearing 8 is located outside the outer periphery 62s of the second eccentric portion 62 on the entire circumference in the circumferential direction. Therefore, the entire circumference of the inner ring 50 is in contact with the washer 12.

The operation of the gear transmission 100 will be described. When torque of a motor (not shown) is transmitted to the input gear 22, the crankshaft 4 rotates around the rotation shaft 30. As the crankshaft 4 rotates, the first eccentric portion 18 rotates eccentrically around the rotation shaft 30. For example, in the case of the first eccentric portion 18 a, the rotation shaft 64 of the first eccentric portion 18 a revolves around the rotation shaft 30. As the first eccentric body 18 rotates eccentrically, the external gear 14 rotates eccentrically around the rotation shaft 32 while meshing with the internal gear 40. The number of teeth of the external gear 14 and the number of teeth of the internal gear 40 (number of internal pins 36) are different. Therefore, when the external gear 14 rotates eccentrically, the carrier 2 supporting the external gear 14 is transferred to the internal gear 40 (case 38) according to the number of teeth difference between the external gear 14 and the internal gear 40. Rotate against. The rotating shaft 32 is also the rotating shaft of the carrier 2.

If the first bearing 16 tries to move in the axial direction (direction of the rotary shaft 30) while the gear transmission 100 is being driven, the retainer 58 of the first bearing 16 contacts the washer 12. Therefore, it is possible to restrict the first bearing 16 from moving in the axial direction while the gear transmission 100 is being driven. The washer 12 is in contact with the inner ring 50 of the second bearing 8. As described above, the second bearing 8 applies a preload that compresses the crankshaft 4 in the direction of the rotation shaft 30. Therefore, a force that presses against the first eccentric portion 18 by the inner ring 50 is applied to the washer 12. For this reason, even when a force is applied from the first bearing 16 to the washer 12, the washer 12 is restricted from moving in the axial direction.

The advantages of the gear transmission 100 will be described with reference to FIGS. 4 and 5 show a part of the

crankshafts

104 and 204. FIG. 4 and 5 correspond to the range shown in FIG. The description of the

crankshafts

104 and 204 may be omitted by giving the same reference numerals having the same or the last two digits to substantially the same parts as the crankshaft 4.

As described above, the crankshaft 4 includes the first eccentric portion 18 and the second eccentric portion 62. The offset amount of the first eccentric portion 18 from the rotation shaft 30 of the rotation shaft 64 is different from the offset amount of the rotation shaft 66 of the second eccentric portion 62 from the rotation shaft 30. As a result, (1) interference between the washer and other components (for example, external gears) can be suppressed, (2) the washer can easily restrict the movement of the first bearing in the axial direction, and (3) the second There is an advantage that the inner ring of the bearing can easily restrict the movement of the washer in the axial direction (see FIGS. 2 and 3). That is, it is possible to reliably restrict the first bearing from moving in the axial direction while suppressing interference between the washer and other components.

4, the rotation shaft of the second eccentric portion 162 is coaxial with the rotation shaft 30 of the shaft portion 6. Further, the diameter of the second eccentric portion 162 is equal to the diameter of the shaft portion 6. In other words, the crankshaft 104 is not provided with the second eccentric portion, and the washer 112 is attached to the shaft portion 6. In the case of the crankshaft 104, since the first bearing 16 is not sufficiently pressed by the washer 112, the movement of the first bearing 16 in the axial direction cannot be sufficiently restricted. That is, the advantage (2) cannot be obtained.

In addition, if the diameter of the washer 112 is increased, the movement of the first bearing 16 in the axial direction can be restricted. However, in that case, a part of the washer 112 is located outside the outer periphery 16s of the first bearing 16, and it is difficult to obtain the advantage (1). Although illustration is omitted, even if the diameter of the second eccentric portion 162 is made larger than the diameter of the shaft portion 6, only the inner diameter of the washer 112 is reduced, and the above advantage (2) cannot be obtained.

5, the rotation shaft of the second eccentric portion 226 is coaxial with the rotation shaft 30 of the shaft portion 6. In the case of the crankshaft 204, the advantage (3) cannot be obtained. As a result, the crankshaft 204 cannot sufficiently restrict the movement of the first bearing 16 in the axial direction. In particular, when the amount of eccentricity of the first eccentric portion 18 (the amount of offset of the rotating shaft 64 with respect to the rotating shaft 30) increases, the diameter of the second eccentric portion 226 increases, and it is difficult to obtain the advantage (3).

In the above embodiment, the inner ring 50 of the second bearing 8 is in contact with the entire circumference of the washer 12, and the washer 12 is in contact with the entire circumference of the first bearing 16 (retainer 58). However, a part of the circumferential direction of the inner ring 50 of the second bearing 8 may not be in contact with the washer 12. Further, the washer 12 may not be in contact with a part of the first bearing 16 in the circumferential direction. What is important is that the crankshaft is provided with two types of eccentric portions (a first eccentric portion and a second eccentric portion engaged with the eccentric rotating gear), and the second eccentric portion is the shaft portion and the first eccentric portion. The eccentric amount of the second eccentric portion with respect to the rotation axis of the crankshaft is smaller than the eccentric amount of the first eccentric portion.

Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

Claims

A crankshaft,
An eccentric rotating gear that rotates eccentrically with rotation of the crankshaft;
A rotating gear that meshes with the eccentric rotating gear and has a different number of teeth from the eccentric rotating gear,
The crankshaft is provided between the shaft portion, the first eccentric portion provided in the middle of the shaft portion and engaged with the eccentric rotation gear, and the second eccentricity provided between the shaft portion and the first eccentric portion. And
The first rotational axis of the first eccentric part is offset by a first distance from the rotational axis of the shaft part;
The second rotational axis of the second eccentric portion is offset by a second distance from the rotational axis of the shaft portion;
A gear transmission in which the second distance is smaller than the first distance.
The gear transmission according to claim 1, wherein the eccentric direction of the second eccentric portion with respect to the shaft portion is the same as the eccentric direction of the first eccentric portion with respect to the shaft portion.
A ring member is attached to the second eccentric part,
The gear transmission according to claim 2, wherein the outer periphery of the ring member is located outside the outer periphery of the first eccentric portion when the crankshaft is observed from the axial direction.
The gear transmission according to claim 3, wherein the outer periphery of the ring member is located outside the outer periphery of the first eccentric portion in the entire periphery.
A first bearing is disposed between the first eccentric portion and the eccentric rotating gear.
The gear transmission according to claim 4, wherein the ring member overlaps with the first bearing in the entire circumference in the circumferential direction when the crankshaft is observed from the axial direction.
A second bearing having an inner ring, a rolling element and an outer ring is attached to the shaft portion,
6. The inner ring of the second bearing is located outside the outer periphery of the second eccentric portion in the entire circumference in the circumferential direction when the crankshaft is observed from the axial direction. Gear transmission.